This invention relates generally to an alarm event generator apparatus, means, system and method and, in particular, to an alarm event generator apparatus, means, system and method for a process control system.
Process control systems may be used to monitor conditions of a manufacturing process and to vary production parameters based on the monitored conditions. A process control system designed for manufacturing circuit boards is described by Yasuhiro Maenishi in U.S. Pat. No. 5,560,533. Maenishi shows that a monitored condition at a location along a production line may be used to change the operating conditions upstream or downstream of the monitored location to prevent a defect occurrence.
The present invention provides a method for an alarm event generation apparatus, means, system and method for an alarm signal for a process control system. The process control system monitors a current production run using a computer system for collecting and storing process data. The process data for the current production run includes a plurality of process parameters. The process parameters are polled from the computer system. Each process parameter has a corresponding manufacturing limit to which it is compared. When a polled process parameter exceeds its corresponding manufacturing limit, an alarm signal is generated. The computer system is prevented from collecting and storing process data while an alarm signal is being generated.
It is to be understood that both the foregoing general description and the following detailed description are exemplary. and do not restrict the invention.
One aspect of the invention is an alarm event generator for a process control system, the process control system includes a computer system for collecting and storing process data, the process data including a plurality of process parameters for a current production run, the alarm event generator comprising: polling means for polling the computer system for the process data including the plurality of process parameters for the current production run; parameter limit generating means for providing a manufacturing limit corresponding to each of the plurality of process parameters; comparing means for comparing at least one of the plurality of process parameters to its corresponding manufacturing limit; alarm generating means for signaling a manufacturing alarm when at least one of the plurality of process parameters exceeds its corresponding manufacturing limit; and control means for preventing the computer system from collecting and storing process data while the alarm generating means is signaling a manufacturing alarm.
Another aspect of the invention is an alarm event generator according to the above description wherein the parameter limit generating means provides a manufacturing limit corresponding to each of the plurality of process parameters by one of (a) calculating the manufacturing limit using process data from previous production runs and (b) receiving the manufacturing limit.
Still another aspect of the invention is an alarm event generator according to the above description wherein the parameter limit generating means provides a manufacturing limit for each of the plurality of process parameters for the current production run by calculating the manufacturing limits using process data from previous production runs according to the following equations:
manufacturing limit=[u+(3{square root over (u)}÷{square root over (v)})]xc3x97product items in current production run
  u  =                                          total            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            process            ⁢                          xe2x80x83                        ⁢            parameter            ⁢                          xe2x80x83                        ⁢            in            ⁢                          xe2x80x83                        ⁢            three                                                            prior            ⁢                          xe2x80x83                        ⁢            production            ⁢                          xe2x80x83                        ⁢            runs                                v  
where v=total number of product items in three prior production runs.
A further aspect of the invention is an alarm event generator according to the above description wherein the parameter limit generating means provides a manufacturing limit and at least one additional limit corresponding to each of the plurality of process parameters; the comparing means compares at least one of the plurality of process parameters to its corresponding manufacturing limit and to its corresponding at least one additional limit; and the alarm generating means signals a manufacturing alarm when one of the plurality of process parameters exceeds its corresponding manufacturing limit and generates an additional alarm corresponding to at least one additional limit being exceeded by the one of the plurality of process parameters.
Another aspect of the invention is an alarm event generator according to the above description wherein one of the at least one additional limits is an engineering limit and the alarm generating means signals an engineering alarm on an engineering interface.
Still another aspect of the invention is an alarm event generator according to the above description wherein an operator interface is capable of executing a foreground task and a background task, the computer system collects process data using a process control task executing as the foreground task while an alarm event generator task is executing as a background task on the operator interface, and while the alarm generating means is signaling a manufacturing alarm the control means prevents the computer system from collecting process data by preventing the process control task from becoming the foreground task.
A further aspect of the invention is an alarm event generator according to the above description wherein when the alarm generating means signals a manufacturing alarm, the alarm event generator task is executing as the foreground task and the computer system is prevented from collecting process data until an operator enters a root cause and a corrective action.
Still a further aspect of the invention is an alarm event generator according to the above description wherein the process is a circuit board manufacturing process and the plurality of process parameters include: open solder defects; insufficient solder defects; solder bridge defects; solder void defects; misalignment defects; missing part defects; billboard defects; upside-down part defects; defective part defects and raised part defects.
Another aspect of the invention is an alarm event generator according to the above description wherein the plurality of process parameters further include: all solder defects; all placement defects: and all other defects.
A further aspect of the invention is a method of generating an alarm for a process control system, the process control system has a computer system for collecting and storing process data, and the process data includes a plurality of process parameters for a production run, the method comprising the steps of: (a) polling the computer system for the process data including the plurality of process parameters for the production run; (b) providing a plurality of manufacturing limits, each corresponding to one of the plurality of process parameters; (c) comparing at least one of the plurality of process parameters to its corresponding manufacturing limit: (d) signaling a manufacturing alarm when at least one of the plurality of process parameters exceeds its corresponding manufacturing limit; and (e) preventing the computer system from collecting and storing process data while the alarm generating means is signaling a manufacturing alarm.
Still another aspect of the invention is a method of generating an alarm according to the above description wherein step (d) comprises the step of signaling an audible manufacturing alarm and signaling a visual manufacturing alarm.
Still a further aspect of the invention is a method of generating an alarm according to the above description wherein the audible manufacturing alarm sounds like a dog barking and the visual manufacturing alarm looks like a attacking dog.
Another aspect of the invention is a method of generating an alarm according to the above description wherein step (b) comprises providing each of the plurality of manufacturing limits by one of (1) calculating the corresponding manufacturing limit using process data from previous production runs and (2) receiving a corresponding manufacturing limit.
Still another aspect of the invention is a method of generating an alarm according to the above description wherein a manufacturing limit is calculated according to the following equations:
xe2x80x83manufacturing limit=[u+(3{square root over (u)}÷{square root over (v)})]xc3x97product items in current production run where
            xe2x80x83        ⁢                  u        =                                                                              total                  ⁢                                      xe2x80x83                                    ⁢                  of                  ⁢                                      xe2x80x83                                    ⁢                  process                  ⁢                                      xe2x80x83                                    ⁢                  parameter                  ⁢                                      xe2x80x83                                    ⁢                  in                  ⁢                                      xe2x80x83                                    ⁢                  three                                                                                                      prior                  ⁢                                      xe2x80x83                                    ⁢                  production                  ⁢                                      xe2x80x83                                    ⁢                  runs                                                              v                    ,              a        ⁢                  xe2x80x83                ⁢        n        ⁢                  xe2x80x83                ⁢        d                  v    =                                        total            ⁢                          xe2x80x83                        ⁢            number            ⁢                          xe2x80x83                        ⁢            of            ⁢                          xe2x80x83                        ⁢            product            ⁢                          xe2x80x83                        ⁢            items            ⁢                          xe2x80x83                        ⁢            in                                                            three            ⁢                          xe2x80x83                        ⁢            prior            ⁢                          xe2x80x83                        ⁢            production            ⁢                          xe2x80x83                        ⁢                          runs              .                                          